Analysis of 22 OCP/OPP Pesticides in Green Tea by GCxGC-TOFMS

Significance of the Topic

The determination of trace pesticide residues in tea is critical for ensuring consumer safety and regulatory compliance. Tea matrices present complex interferences that challenge conventional chromatographic methods. Comprehensive two-dimensional gas chromatography coupled with time-of-flight mass spectrometry (GC×GC-TOFMS) offers enhanced separation and sensitivity, making it a valuable approach for multiresidue analysis in food samples.

Objectives and Overview

This study aimed to develop and demonstrate a GC×GC-TOFMS method for the simultaneous analysis of 22 organochlorine and organophosphorus pesticides in green tea. The approach focused on achieving baseline separation at sub-ng/kg levels and generating a detailed multidimensional chromatographic profile.

Methodology and Instrumentation

• Sample Preparation and Spiking
  Standard green tea samples were spiked at 500 parts-per-trillion (ppt) concentration for all 22 target pesticides to assess method performance.
• Chromatographic Conditions
  • First-dimension column: 10 m × 0.18 mm, 0.2 µm Rtx-5
  • Second-dimension column: 1.5 m × 0.10 mm, 0.1 µm DB-17
• Detection by TOFMS
  • Mass range: m/z 45–550
  • Spectral acquisition rate: 150 spectra/s

Main Results and Discussion

The GC×GC-TOFMS analysis produced a three-dimensional chromatographic area representation showing clear resolution of all 22 pesticides at 500 ppt spiking level. Enhanced peak capacity of the two-dimensional separation enabled discrimination of coeluting compounds typically unresolved by one-dimensional GC. The high acquisition rate of TOFMS facilitated accurate mass spectral deconvolution and reliable identification in the complex tea extract.

Benefits and Practical Applications

• Improved Selectivity: GC×GC reduces coelution and matrix interferences, enhancing detection confidence.
• High Sensitivity: Sub-ng/kg level quantification supports stringent regulatory limits.
• Comprehensive Profiling: Three-dimensional chromatograms provide detailed compound mapping in complex matrices.
• Versatility: Applicable to a wide range of pesticide classes in various food samples.

Future Trends and Potential Applications

• Integration with High-Resolution Mass Spectrometry: Further increase in selectivity and quantitation accuracy.
• Automated Data Processing: Advanced algorithms for rapid peak deconvolution and reporting.
• Miniaturized and Portable GC×GC Systems: Enabling on-site screening of contaminants.
• Expansion to Other Matrices: Application to environmental, pharmaceutical, and clinical samples.

Conclusion

GC×GC-TOFMS offers a powerful solution for trace-level pesticide analysis in complex food matrices such as green tea. The method demonstrates excellent separation, sensitivity, and reliability for monitoring organochlorine and organophosphorus residues. Its comprehensive profiling capabilities and adaptability position it as a valuable tool in food safety laboratories and regulatory environments.

Instrumental Setup

• GC×GC Columns: 10 m × 0.18 mm × 0.2 µm Rtx-5 and 1.5 m × 0.10 mm × 0.1 µm DB-17
• TOFMS: Mass range 45–550 m/z, acquisition rate of 150 spectra/second